This study is designed to: 1) identify risk factors of severe acute chest syndrome (ACS) and chronic pain in children with sickle cell disease (SCD), 2) develop a clinical score for ACS based on clinical severity, 3) evaluate the role of endothelin-1 and phospholipase A2, biologic markers of inflammation and vascular tone, and 4) develop a clinical staging system for chronic pulmonary changes in children with SCD. Kim Smith-Whitley, M.D., Assistant Professor of Pediatrics at the University of Pennsylvania School of Medicine and an attending physician in the Department of Hematology at the Children's Hospital of Philadelphia (CHOP), will design and conduct this study over five years. This project is an ideal vehicle for Dr. Smith-Whitley to develop the skills she will need to become an independent clinical researcher. She will work under the direction of Kwaku Ohene-Frempong, M.D., an international expert in SCD and Director of the Comprehensive Sickle Cell Center at CHOP. In this academic institution, Dr. Ohene-Frempong will provide direction in clinical research study design and management as well as expertise in academic medicine career development, clinical teaching skills, and program administration. He will also contribute his expertise in the clinical care of children with SCD at an institution that provides health care services for over 500 children with SCD. Through this interaction, Dr. Smith-Whitley will be able to learn invaluable skills in clinical project design and performance from conception to completion and publication and develop educational and administrative skills that will allow her to pursue a career in academic medicine as a pediatric hematologist and an independent clinical researcher.